Optoelectronic device and the manufacturing method thereof

ABSTRACT

One aspect of the present disclosure provides an optoelectronic device comprising a substrate; a first window layer on the substrate, having a first sheet resistance, a first thickness, and a first impurity concentration; a second window layer having a second sheet resistance, a second thickness, and a second impurity concentration; and a semiconductor system between the first window layer and the second window layer; wherein the second window layer comprises a semiconductor material different from the semiconductor system, and the second sheet resistance is greater than the first sheet resistance. 
     One aspect of the present disclosure provides a method for manufacturing an optoelectronic device in accordance with the present disclosure. The method comprises the steps of providing a substrate; forming a semiconductor system on the substrate; forming a window layer on the semiconductor system, wherein the window layer comprises a semiconductor material different from the semiconductor system; selectively removing the window layer thereby forming a width difference between the window layer and the semiconductor system, and the width difference is greater than 1 micron.

RELATED APPLICATION DATA

This application claims priority to U.S. provisional application No.61/302,662, filed Feb. 9, 2010, entitled “OPTOELECTRONIC SEMICONDUCTORDEVICE AND THE MANUFACTURING METHOD THEREOF”, and the contents of whichare incorporated herein by reference.

BACKGROUND Technical Field

The application relates to an optoelectronic device and themanufacturing method thereof.

Recently, efforts have been put to promote the luminous efficiency ofthe light-emitting diode (LED) in order to implement the device in thelighting field, and further conserve the energy and reduce carbonemission. The LED luminous efficiency can be increased through severalaspects. One is to increase the internal quantum efficiency (IQE) byimproving the epitaxy quality to enhance the combination efficiency ofelectrons and holes. Another is to increase the light extractionefficiency (LEE) that emphasizes on the increase of light which isemitted by the light-emitting layer capable of escaping outside thedevice, and therefore reducing the light absorbed by the LED structure.

SUMMARY

The present disclosure provides a novel structure and the manufacturingmethod thereof for increasing the light extraction efficiency.

One aspect of the present disclosure provides an optoelectronic devicecomprising a substrate; a first window layer on the substrate having afirst sheet resistance, a first thickness, and a first impurityconcentration; a second window layer having a second sheet resistance, asecond thickness, and a second impurity concentration; and asemiconductor system between the first window layer and the secondwindow layer; wherein the second window layer comprises a semiconductormaterial different from the semiconductor system, and the second sheetresistance is greater than the first sheet resistance.

One aspect of the present disclosure provides an optoelectronic devicecomprising a substrate; a metal layer comprising a metal element on thesubstrate; a first window layer comprising the metal element; and atransparent conductive layer between the metal layer and the firstwindow layer; wherein an atomic concentration of the metal element inthe first window layer is less than 1*10¹⁹ cm⁻³.

One aspect of the present disclosure provides an optoelectronic devicecomprising a substrate; an n-type window layer on the substrate; asemiconductor system on the n-type window layer; a p-type window layeron the semiconductor system; wherein the optoelectronic device emitsamber or red light with an optical efficiency at least 70 lumen/watt ata driving current density ranging from 0.1˜0.32 mA/mil².

One aspect of the present disclosure provides a method for manufacturingan optoelectronic device in accordance with the present disclosure. Themethod comprises the steps of providing a substrate; forming asemiconductor system on the substrate; forming a window layer on thesemiconductor system, wherein the window layer comprises a semiconductormaterial different from the semiconductor system; selectively removingthe window layer thereby forming a width difference between the windowlayer and the semiconductor system, and the width difference is greaterthan 1 micron.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1H illustrate the corresponding structures fabricated by themanufacturing method step-by-step according to one embodiment of thepresent disclosure.

FIG. 2 illustrates an optoelectronic device according to one embodimentof the present disclosure.

FIG. 3 illustrates an SEM photograph of the optoelectronic device inaccordance with the present disclosure.

FIG. 4 illustrates a top view of the first ohmic contact layer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1A to 1H show the corresponding structures fabricated by themanufacturing method step-by-step according to one embodiment of thepresent disclosure. With reference to FIG. 1A, the method formanufacturing an optoelectronic device in accordance with the presentdisclosure comprises a step of providing a substrate 101, such as agrowth substrate for growing or carrying an optoelectronic system 120,and the material for the substrate 101 includes but is not limited togermanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), galliumphosphide (GaP), sapphire, silicon carbide (SiC), silicon (Si), lithiumaluminum oxide (LiAlO₂), zinc oxide (ZnO), gallium nitride (GaN),aluminum nitride (AlN), glass, composite, diamond, CVD diamond,diamond-like carbon (DLC), and so on.

a first window layer 111 is formed on the substrate 101 made of amaterial containing at least one element selected from the groupconsisting of Al, Ga, In, As, P, and N, such as GaN, AlGaInP or anyother suitable materials. The first window layer 111 is a layer with aconductivity-type, such as n-type or p-type(Al_(x)Ga_((1-x)))_(0.5)In_(0.5)P where 0.5≦x≦0.8. The first windowlayer 111 has two opposite surface wherein the first surface of thefirst window layer 111 is closer to the substrate 101.

A transition layer could be optionally formed between the substrate 101and the first window layer 111. The transition layer between twomaterial systems can be used as a buffer system. For the structure ofthe light-emitting diode, the transition layer is used to reduce thelattice mismatch between two material systems. On the other hand, thetransition layer could also be a single layer, multiple layers, or astructure to combine two materials or two separated structures where thematerial of the transition layer can be organic, inorganic, metal,semiconductor, and so on, and the structure can be a reflection layer, aheat conduction layer, an electrical conduction layer, an ohmic contactlayer, an anti-deformation layer, a stress release layer, a stressadjustment layer, a bonding layer, a wavelength converting layer, amechanical fixing structure, and so on.

Next, the optoelectronic system 120 is formed on the second surface ofthe first window layer 111 including at least a first layer 121 having afirst conductivity-type, a conversion unit 122, and a second layer 123having a second conductivity-type in sequence. The first layer 121 andthe second layer 123 are two single-layer structures or two multiplelayers structure (“multiple layers” means two or more than two layers)having different conductivities, electrical properties, polarities,and/or dopants for providing electrons or holes respectively. If thefirst layer 121 and the second layer 123 are composed of semiconductormaterials, such as (Al_(x)Ga_((1-x)))_(0.5)In_(0.5)P where 0.5≦x≦0.8,the first or second conductivity-type can be p-type or n-type. The firstwindow layer 111 has the same conductivity-type with the first layer121, such as n-type. Besides, the first window layer 111 has greaterimpurity concentration than the first layer 121 to have a betterconductivity. The conversion unit 122 disposed between the first layer121 and the second layer 123 is a region where the light energy and theelectrical energy could transfer or could be induced to transfer. Theoptoelectronic system 120, such as applied to a semiconductor device,equipment, product, circuit, can proceed or induce the light energy andelectrical energy transfer. Specifically speaking, the optoelectronicsystem includes at least one of a light-emitting diode (LED), a laserdiode (LD), a solar cell, a liquid crystal display, or an organiclight-emitting diode. The optoelectronic system having the conversionunit 122 transferring the electrical energy to the light energy is alight-emitting diode, a liquid crystal display, or an organiclight-emitting diode. The optoelectronic system having the conversionunit 122 transferring the light energy to the electrical energy is asolar cell or an optoelectronic diode. The phrase “optoelectronicsystem” in the specification does not require that all the sub-systemsor units in the system manufactured by semiconductor materials. Othernon-semiconductor materials such as metal, oxide, insulator, and so oncould also be selectively integrated in this optoelectronic system 120.

Taking the light-emitting diode as an example, the emission spectrum ofthe transferred light could be adjusted by changing the physical orchemical arrangement of one layer or more layers in the optoelectronicsystem 120. The commonly used materials are the series of aluminumgallium indium phosphide (AlGaInP), the series of aluminum galliumindium nitride (AlGaInN), the series of zinc oxide (ZnO), and so on. Theconversion unit 122 can be a single heterostructure (SH) structure, adouble heterostructure (DH) structure, a double-side doubleheterostructure (DDH) structure, or a multi-quantum well (MWQ)structure. Specifically, the conversion unit 122 comprises a MQWstructure comprising a plurality of barrier layers and well layersalternately stacked, each of the barrier layers comprises(Al_(y)Ga_((1-y)))_(0.5)In_(0.5)P where 0.5≦y≦0.8; and each of the welllayers comprises In_(0.5)Ga_(0.5)P. Besides, the wavelength of theemitted light could also be adjusted by changing the number of the pairsof the quantum well or the composition of the barrier layer, e.g. theemitted light is red light with dominant wavelength between 600 and 630nm by having y around 0.7 or amber light with dominant wavelengthbetween 580 and 600 nm by having y around 0.55.

Forming a second window layer 112 on a first surface of theoptoelectronic system 120 whose material contains at least one elementselected from the group consisting of Al, Ga, In, As, P, and N, such asGaN, AlGaInP or any other suitable materials, and the second windowlayer 112 comprises at least one material different from theoptoelectronic semiconductor system or the second layer 123. The secondwindow layer 112 is preferred a layer with a conductivity-type the samewith the second layer 123, such as a p-type GaP layer. In anotherembodiment, the sidewall of the second window layer 112 and/or thesemiconductor system 120 need not be orthogonal to the substrate, butrather may be oblique thereto as indicated in FIG. 3.

Then, forming a first ohmic contact layer 130 formed by conductivematerial such as BeAu or GeAu alloy on the second window layer 112, andtherefore forming a first stack 10 structure as shown in FIG. 1A,wherein the first ohmic contact layer 130 comprises a plurality offingers 132 extending toward borders of the first stack 10 structure asshown in FIG. 4. A first alloying process is then performed at analloying temperature of around 300˜500° C. or more for forming an ohmiccontact between the first ohmic contact layer 130 and the second windowlayer 112. The detail of the alloying process is well-known for thoseskilled in this field, and not necessarily disclosed herein.

Next, bonding a temporary substrate 102 formed by supportive materialsuch as glass to the first ohmic contact layer 130 and the second windowlayer 112 of the first stack structure 10 as shown in FIG. 1B, andremoving the substrate 101, and therefore exposing the first surface ofthe first window layer 111 as shown in FIG. 1C.

Next, forming a second ohmic contact layer 140 formed by conductivematerial like GeAu or BeAu alloy on the first surface of the firstwindow layer 111, and therefore forming a second stack structure asshown in FIG. 1D, wherein the second ohmic contact layer 140 comprises aplurality of dots that are arranged in a two-dimensional array and ispreferred substantially do not overlap with the first ohmic contactlayer 130 in vertical direction as shown in FIGS. 1D and 4 for bettercurrent spreading effect. A second alloying process is then performed atan alloying temperature of around 300˜500° C. or more for forming anohmic contact between the second ohmic contact layer 140 and the firstwindow layer 111. The detail of the alloying process is well-known forthose skilled in this field, and not necessarily disclosed herein.

Next, a transparent conductive layer 141 is sequentially formed bye-beam or sputtering to cover the second ohmic contact layer 140,wherein the material of the transparent conductive layer 141 comprisesmetal oxide, such as at least one material selected from the groupconsisting of indium tin oxide (ITO), cadmium tin oxide (CTO), antimonytin oxide, indium zinc oxide, zinc aluminum oxide, and zinc tin oxide;and the thickness is about 0.005 μm˜0.6 μm, 0.005 μm˜0.5 μm, 0.005μm˜0.4 μm, 0.005 μm˜0.3 μm, 0.005 μm˜0.2 μm, 0.2 μm˜0.5 μm, 0.3 μm˜0.5μm, 0.4 μm˜0.5 μm, 0.2 μm˜0.4 μm, or 0.2 μm˜0.3 μm.

Next, a reflecting layer 150 is formed with a conductive materialcomprising metal, such as Ag, on the transparent conductive layer 141 asshown in FIG. 1E, and then the reflecting layer 150 is bonded to asupporting substrate 103 by a metal layer 160 as shown in FIG. 1F. Inthis embodiment, the supporting substrate 103 comprises Si, and themetal layer 160 served as a bonding layer comprises at least onematerial selected from the group consisting of In, Au, Sn, Pb, InAu,SnAu, and the alloy thereof.

Next, the temporary substrate 102 is removed to expose the first ohmiccontact layer 130 and the second window layer 112, and therefore forminga third stack structure. Then the third stack structure is patterned bythe lithographic-etching process to form a plurality of chip areas (notshown) on the supporting substrate 103, wherein the etchants of theetching process, e.g. dry-etching chemicals comprising fluoride orchloride etch the second window layer 112 relatively faster than theoptoelectronic system 120 such that a first mesa region S1 is formed onthe surface of the optoelectronic system 120 or the second layer 123,and the width of the optoelectronic system 120 or the second layer 123is larger than the width of the second window layer 112 at the interfaceof the optoelectronic system 120 or the second layer 123 and the secondwindow layer 112 as indicated in FIG. 1G. It can also be noted that asecond mesa region S2 is formed on the surface of the first window layer111, and the bottom width of the first window layer 111 is larger thanthe optoelectronic system 120 or the first layer 121.

Next, at least the exposed top and sidewall surfaces of the secondwindow layer 112 is wet etched such that the exposed top and sidewallsurfaces of the second window layer 112 are roughened, wherein theetching solution, such as a mixture of hydrofluoric acid (HF), nitricacid (HNO₃), and acetic acid (CH₃COOH), etches the second window layer112 relatively faster than the optoelectronic system 120 such that thewidth difference L1 is further expanded and become larger, and thesecond window layer 112 has an enhanced surface roughness higher thanthat of the optoelectronic system 120, and wherein the width differenceL1 is greater than 1 micron and/or less than 10 microns as indicated inFIG. 1H or FIG. 3.

Finally, a first pad 171 is formed on the first ohmic contact layer 130,a second pad 172 is formed on the supporting substrate 103, and apassivation layer 180 covers the second window layer 112 and the firstohmic contact layer 130 to form the optoelectronic device in accordancewith the present disclosure as shown in FIG. 2. The passivation layer180 serves as a protection layer to protect the optoelectronic devicefrom environment damage, such as moisture, or mechanical damage. The SEMphotograph of the optoelectronic device according to one embodiment ofthe present disclosure is demonstrated as in FIG. 3. According to oneembodiment of the present disclosure, the first window layer 111comprises semiconductor material, such as(Al_(x)Ga_((1-x)))_(0.5)In_(0.5)P where 0.5≦x≦0.8, and the reflectinglayer 150 comprising a metal element, e.g. Ag, is formed after the firstand second alloying process such that the metal element in thereflecting layer is less diffused into the first window layer 111, wherethe first window layer 111 comprises a semiconductor material, preferreda material with substantially the same composition to the first layer121. According to another embodiment of the present disclosure, theatomic concentration of the metal element in the first window layer isless than 1*10¹⁷ cm⁻³ and the atomic concentration of the metal elementis greater than 1*10¹⁶ cm⁻³, therefore causing less degradation to thereflecting layer. The reflecting layer has a reflectivity greater than90%.

Table 1 shows the optical efficiencies tested under given conditions bythe optoelectronic device of the present disclosure. For anoptoelectronic device with a small chip size, such as 10 mil², theoptical efficiency is as high as about 70 lumen/watt under 20 mA or 0.2mA/mil² of driving current. For an optoelectronic device with a relativesmaller chip size, such as 14 mil², the optical efficiency is as high asabout 100 lumen/watt under 20 mA or 0.1 mA/mil² of driving current. Foran optoelectronic device with a relative larger chip size, such as 28mil², the optical efficiency is as high as about 106 lumen/watt under250 mA or 0.32 mA/mil² of driving current. For an optoelectronic devicewith a large chip size, such as 42 mil², the optical efficiency is ashigh as about 121 lumen/watt under 350 mA or 0.2 mA/mil² of drivingcurrent. It can be observed from table 1 that the optoelectronic deviceaccording to the embodiment of the present disclosure achieves anoptical efficiency at least 70 lumen/watt, or preferred at least 100lumen/watt at a driving current density ranging from 0.1˜0.32 mA/mil².

TABLE 1 the optical efficiencies tested under given conditions accordingto the optoelectronic device of the present disclosure. OperatingCurrent Optical Dominant Chip size current density efficiency wavelength[mil ²] [mA] [mA/mil²] [lumen/watt] [nm] 10 20 0.2 ~70 ~620 14 20 ~0.1~90 ~620 28 250 ~0.32 ~106 ~613 42 350 ~0.2 ~121 ~613

According to the present disclosure, the sheet resistance of the firstwindow layer 111 is higher than that of the second window layer 112.Also, the second ohmic contact layer 140 substantially does not overlapwith the first ohmic contact layer 130 in vertical direction. Therefore,the driving current is crowding nearby the second ohmic contact layer140. The light emittied by the optoelectronic device is corresponding tothe region of the second ohmic contact layer 140 and is not blocked bythe first ohmic contact layer 130, and therefore having the effect ofcurrent blocking and benefit to lateral current spreading.

According to another embodiment of the present disclosure, the firstwindow layer 111 comprises a lower impurity concentration than that ofthe second window layer 112 to have a lower sheet resistance than thatof the second window layer 112. According to another embodiment of thepresent disclosure, the first window layer 111 comprises an n-typeimpurity with an impurity concentration of around 1×10¹⁷ 5×10¹⁷ cm⁻³,and the second window layer 112 comprises a p-type impurity with animpurity concentration of 1×10¹⁸˜5×10¹⁸ cm⁻³ higher than that of thefirst window layer 111. According to another embodiment of the presentdisclosure, the thickness of the first window layer between 1˜5 micronsis smaller than the thickness of the second window layer 112 between5˜20 microns.

According to one embodiment of the present disclosure, because thesidewall surfaces of the second window layer 112 are roughened, thelight can be laterally extracted easily. The chip areas can be rectanglein shape for better luminous efficiency. The ratio of the length to thewidth of the rectangle is preferred from 1.5:1 to 10:1.

It will be apparent to those having ordinary skill in the art thatvarious modifications and variations can be made to the devices inaccordance with the present disclosure without departing from the scopeor spirit of the disclosure. In view of the foregoing, it is intendedthat the present disclosure covers modifications and variations of thisdisclosure provided they fall within the scope of the following claimsand their equivalents.

Although the drawings and the illustrations above are corresponding tothe specific embodiments individually, the element, the practicingmethod, the designing principle, and the technical theory can bereferred, exchanged, incorporated, collocated, coordinated except theyare conflicted, incompatible, or hard to be put into practice together.

Although the present application has been explained above, it is not thelimitation of the range, the sequence in practice, the material inpractice, or the method in practice. Any modification or decoration forpresent application is not detached from the spirit and the range ofsuch.

1. An optoelectronic device comprising: a substrate; a first windowlayer on the substrate, having a first sheet resistance, a firstthickness, and a first impurity concentration; a second window layerhaving a second sheet resistance, a second thickness, and a secondimpurity concentration; and a semiconductor system between the firstwindow layer and the second window layer; wherein the second windowlayer comprises a semiconductor material different from thesemiconductor system, and the second sheet resistance is lower than thefirst sheet resistance.
 2. The optoelectronic device of claim 1, whereinthe semiconductor system comprises a first semiconductor layer of firstconductivity-type, a second semiconductor layer of secondconductivity-type, and a conversion unit between the first semiconductorlayer and the second semiconductor layer.
 3. The optoelectronic deviceof claim 1, wherein a width difference between a width of the secondwindow layer and a width of the semiconductor system, and is greaterthan 1 micron.
 4. The optoelectronic device of claim 1, wherein thesecond thickness is greater than the first thickness, and/or the secondimpurity concentration is greater than the first impurity concentration.5. The optoelectronic device of claim 1, wherein the top and sidewallsurfaces of the second window layer are rough.
 6. The optoelectronicdevice of claim 1, wherein the second window layer comprises p-typesemiconductor material.
 7. The optoelectronic device of claim 1, furthercomprising a transparent conductive layer between the substrate and thefirst window layer.
 8. The optoelectronic device of claim 7, wherein thetransparent conductive layer comprises metal oxide.
 9. Theoptoelectronic device of claim 8, further comprising a metal reflectorbetween the substrate and the transparent conductive layer.
 10. Anoptoelectronic device comprising: a substrate; a metal layer comprisinga metal element on the substrate; a first window layer comprising themetal element; and a transparent conductive layer between the metallayer and the first window layer; wherein an atomic concentration of themetal element in the first window layer is less than 1*10¹⁹ cm⁻³. 11.The optoelectronic device of claim 10, further comprising asemiconductor system comprises a first semiconductor layer of firstconductivity-type, a second semiconductor layer of secondconductivity-type, and a conversion unit between the first semiconductorlayer and the second semiconductor layer.
 12. The optoelectronic deviceof claim 10, wherein the metal element comprises silver.
 13. Theoptoelectronic device of claim 10, wherein an atomic concentration ofthe metal element in the first window layer is less than 1*10¹⁷ cm⁻³.14. The optoelectronic device of claim 10, wherein an atomicconcentration of the metal element in the first window layer is greaterthan 1*10¹⁶ cm⁻³.
 15. The optoelectronic device of claim 10, wherein thetransparent conductive layer comprises metal oxide.
 16. Theoptoelectronic device of claim 10, wherein the metal layer has areflectivity greater than 90%.
 17. The optoelectronic device of claim10, further comprising a second window layer with a rough surface on thesemiconductor system.
 18. The optoelectronic device of claim 10, whereina width of the window layer is different from a width of thesemiconductor system thereby forming a width difference, and the widthdifference is greater than 1 micron.
 19. An optoelectronic devicecomprising: a substrate; a n-type window layer on the substrate; asemiconductor system on the n-type window layer; and a p-type windowlayer one the semiconductor system; wherein the optoelectronic deviceemits amber or red light with an optical efficiency at least 70lumen/watt at a driving current density ranging from 0.1˜0.32 mA/mil².20. A method for manufacturing an optoelectronic device comprising thesteps of: providing a substrate; forming a semiconductor system on thesubstrate; forming a window layer on the semiconductor system, whereinthe window layer comprises a semiconductor material different from thesemiconductor system; and selectively removing the window layer therebyforming a width difference between the window layer and thesemiconductor system, and the width difference is greater than 1 micron.